Non-Destructive Calibration Scheme for Online Monitoring Device of Metal Oxide Arrester

The reliability of online monitoring device for metal oxide arrester (MOA) is the prerequisite for ensuring the MOA normal operation. For online monitoring device, this paper proposes the non-destructive calibration scheme which can improve maintenance efficiency. The on-site calibration device consists of current source, ammeter, micro-current detector and control unit. There are two key technologies involved in the on-site calibration device, the one is the phase locked loop (PLL) for current source, the other is the high precision current detection for ammeter and micro-current detector. The proposed PLL of the reference voltage can generate low delay orthogonal signals and eliminate the second harmonic disturbances caused by the crystal oscillator error of microcontroller unit (MCU). The experimental results show the effectiveness of the proposed calibration scheme.